>What is the console for the powermac port? is it openfirmware via the serial port?

Yes.  I am using serial console.

>I have yet to get my other computers moved next to the powermac but still am
>not certain if openfirmware will work because the modem port is "connected" to
>the built-in modem, Will openfirmware work on the printer port in this case??

You can set input-device and output-device to ttyb to use the printer port.
(at least, my PM9600 works.)